CODEWITHSUNDEEP
c#.netgenerics
Francisco Ryan Tolmasky I
Francisco Ryan Tolmasky I

Reputation: 6173

Can't implement both GetEnumerator return IEnumerator AND IEnumerator<T> when implementing ICollection<T>

I'm writing a simple collection class that implements ICollection<T>. Everything basically works except if I add a IEnumerator<T> GetEnumerator() method it complains I don't have an IEnumerator GetEnumerator() method. And vice versa. I'm not allowed to have both since they differ only in return type, so I'm really quite confused as to what the compiler wants from me.

Here are the errors precisely as they are given to me:

error CS0738: MyClass<T>' does not implement interface memberSystem.Collections.Generic.IEnumerable.GetEnumerator()' and the best implementing candidate MyClass<T>.GetEnumerator()' return typeSystem.Collections.IEnumerator' does not match interface member return type `System.Collections.Generic.IEnumerator'

OR, alternatively I can have:

error CS0738: MyClass<T>' does not implement interface memberSystem.Collections.IEnumerable.GetEnumerator()' and the best implementing candidate MyClass<T>.GetEnumerator()' return typeSystem.Collections.Generic.IEnumerator' does not match interface member return type `System.Collections.IEnumerator'

Upvotes: 2

Views: 2189

Answers (3)

Simon Whitehead
Simon Whitehead

Reputation: 65049

Implement them explicitly:

IEnumerator IEnumerable.GetEnumerator() {
}

IEnumerator<T> IEnumerable<T>.GetEnumerator() {
}

// etc.

Explicit interface implementation is how this is achieved. Read about it on MSDN: http://msdn.microsoft.com/en-us/library/aa288461(v=vs.71).aspx

Upvotes: 6

MarcinJuraszek
MarcinJuraszek

Reputation: 125610

Use explicit interface implementation. That's exactly how List<T> implements both IEnumerable and IEnumerable<T>, pointing to third GetEnumerator method:

IEnumerator IEnumerable.GetEnumerator()
{
    return new List<T>.Enumerator(this);
}

IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
    return new List<T>.Enumerator(this);
}

public List<T>.Enumerator GetEnumerator()
{
    return new List<T>.Enumerator(this);
}

With that kind of declaration you can have couple methods with the same name - as long as they implement some interface method.

Upvotes: 3

ohmusama
ohmusama

Reputation: 4215

ICollection extends IEnumerable. Thus you don't want to do IEnumerable on your class

http://msdn.microsoft.com/en-us/library/92t2ye13.aspx

Upvotes: -3

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